Aspects of the invention can relate to an image display device and a projector.
Improvements in picture quality of a related art electronic display device, such as an LCD (liquid crystal display), an EL (electro-luminescence) display, a plasma display, a CRT (cathode ray tube) and a projector have been remarkable and a device having a property such that resolution and the color gamut are almost equal to a visual characteristic of a human being has been almost put into practice. As for an intensity dynamic range, however, a reproduction range is generally at most around from 1 to 102 [nits] while a gradation number is 8 bits. On the other hand, as for human eyesight, it is said that an intensity dynamic range capable of perception at one time is around from 102 to 104 [nits] while intensity distinction ability is 0.2 [nits], which can be converted into 12 bits in gradation number. When a display image of a current display device is considered from a viewpoint of such a visual characteristic, narrowness of the intensity dynamic range is conspicuous in addition to lack of gradation of a shadow part or a highlighted part, so that the display image is not satisfied in reality and power.
In CG (computer graphics) used in movie films, games and the like, there has almost been a mainstream of the tendency to pursue reality in drawing with image data having an intensity dynamic range and a gradation characteristic, which are close to human eyesight, (refer to as HDR (high dynamic range) image data, hereinafter). A display device, however, lacks the performance for displaying the above. This causes a problem that expression ability, which is inherent in CG contents, cannot be sufficiently shown.
Further, in the next-generation OS (operating system), 16 bits of color space is planned to be adopted. This causes a dynamic range and a gradation number to be greatly increased, comparing with a case of using the current 8-bits color space. Accordingly, it is expected that a need for an electronic display device, which is capable of making the best use of the 16-bits color space and which has a high dynamic range and a high gradation, will be increased.
Among display devices, a projecting type of display device, such as a liquid crystal projector and a DLP (digital light processing, a registered trademark of the TI company) projector is a display device capable of large-screen display and effective for reproducing reality and power of a display image. In such a field of art, the following proposal has been made for the purpose of solving the above problems.
For a related or display device having a high dynamic range, there is a technique disclosed in, for example, Japanese Patent Application Publication 2001-100689. In the technique, a display device can include a light source, a second optically modulating device for modulating intensity of a whole wavelength range of light and a first optically modulating device for modulating intensity of respective wavelength ranges of the three primary colors RGB in the wavelength region of light and, in the display device, the light from the light source is modulated by technique of the second optically modulating device to form desired distribution of intensity, an optical image so formed is formed on a display surface of the first optically modulating device to be color-modulated and the secondarily modulated light is projected. Respective pixels of the second optically modulating device and the first optically modulating device are individually controlled on the basis of a first controlling value and a second controlling value, respectively, the first and second controlling values being determined on the basis of HDR display data. For the optically modulating device, used is a transmission type of modulating device, which has a pixel structure or a segment structure capable of individually controlling transmittance and which can control two-dimensional distribution of transmittance. As a typical example of the above, a liquid crystal light valve can be named. Moreover, a reflecting type of modulating device may be used instead of the transmission type of modulating device. A DMD (digital micro-mirror device) can be named as a typical example of the reflecting type of modulating device.
Here, considered is a case of using an optically modulating device in which transmittance in dark display is 0.2% while transmittance in bright display is 60%. An intensity dynamic range of a single optically modulating device is 60/0.2=300. Such a display device is equivalent to optically modulating devices, which have the intensity dynamic range of 300 and which are optically arranged in series. Accordingly, it is possible to obtain the intensity dynamic range of 300×300=90000. The same idea can be applied to a gradation number. Arranging optically in series optically modulating devices, which have an 8-bits gradation, allows a gradation number more than 8 bits to be obtained.
In the above description, Japanese Patent Application Publication 2001-100689 is an example of related art.